Re: [PATCH v4 8/8] tty: i3c: add TTY over I3C master support

Ilpo Järvinen
2024-01-27T19:53:01Z

On Tue, 23 Jan 2024, Frank Li wrote:

> In typical embedded Linux systems, UART consoles require at least two pins,
> TX and RX. In scenarios where I2C/I3C devices like sensors or PMICs are
> present, we can save these two pins by using this driver. Pins is crucial
> resources, especially in small chip packages.
>
> This introduces support for using the I3C bus to transfer console tty data,
> effectively replacing the need for dedicated UART pins. This not only
> conserves valuable pin resources but also facilitates testing of I3C's
> advanced features, including early termination, in-band interrupt (IBI)
> support, and the creation of more complex data patterns. Additionally,
> it aids in identifying and addressing issues within the I3C controller
> driver.
>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
>
> Notes:
> Notes:
> Version number use i3c target patches.
> Change from v3 to v4
> - add static at i3c_remove()
> Change v2
> - using system_unbound_wq working queue
> - fixed accoring to Jiri Slaby's comments
>
> Change before send with i3c target support
>
> Change from v4 to v5
> - send in i3c improvememtn patches.
>
> Change from v2 to v4
> - none
>
> Change from v1 to v2
> - update commit message.
> - using goto for err handle
> - using one working queue for all tty-i3c device
> - fixed typo found by js
> - update kconfig help
> - using kfifo
>
> Still below items not be fixed (according to Jiri Slaby's comments)
> - rxwork thread: need trigger from two position.
> - common thread queue: need some suggestion
>
> drivers/tty/Kconfig | 13 ++
> drivers/tty/Makefile | 1 +
> drivers/tty/i3c_tty.c | 426 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 440 insertions(+)
> create mode 100644 drivers/tty/i3c_tty.c
>
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 5646dc6242cd9..9ab4cd480e9f8 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -412,6 +412,19 @@ config RPMSG_TTY
> To compile this driver as a module, choose M here: the module will be
> called rpmsg_tty.
>
> +config I3C_TTY
> + tristate "TTY over I3C"
> + depends on I3C
> + help
> + Select this option to use TTY over I3C master controller.
> +
> + This makes it possible for user-space programs to send and receive
> + data as a standard tty protocol. I3C provide relatively higher data
> + transfer rate and less pin numbers, SDA/SCL are shared with other
> + devices.
> +
> + If unsure, say N
> +
> endif # TTY
>
> source "drivers/tty/serdev/Kconfig"
> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
> index 07aca5184a55d..f329f9c7d308a 100644
> --- a/drivers/tty/Makefile
> +++ b/drivers/tty/Makefile
> @@ -27,5 +27,6 @@ obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o
> obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
> obj-$(CONFIG_VCC) += vcc.o
> obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o
> +obj-$(CONFIG_I3C_TTY) += i3c_tty.o
>
> obj-y += ipwireless/
> diff --git a/drivers/tty/i3c_tty.c b/drivers/tty/i3c_tty.c
> new file mode 100644
> index 0000000000000..8f4e87dfa01cd
> --- /dev/null
> +++ b/drivers/tty/i3c_tty.c
> @@ -0,0 +1,426 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2023 NXP.
> + *
> + * Author: Frank Li <Frank.Li@nxp.com>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/i3c/device.h>
> +#include <linux/i3c/master.h>
> +#include <linux/slab.h>
> +#include <linux/console.h>
> +#include <linux/serial_core.h>
> +#include <linux/interrupt.h>

Do you need this header.

> +#include <linux/workqueue.h>
> +#include <linux/tty_flip.h>
> +
> +static DEFINE_IDR(i3c_tty_minors);
> +static DEFINE_MUTEX(i3c_tty_minors_lock);
> +
> +static struct tty_driver *i3c_tty_driver;
> +
> +#define I3C_TTY_MINORS 8
> +#define I3C_TTY_TRANS_SIZE 16
> +#define I3C_TTY_RX_STOP 0
> +#define I3C_TTY_RETRY 20
> +#define I3C_TTY_YIELD_US 100
> +
> +struct ttyi3c_port {
> + struct tty_port port;

Missing #include

> + int minor;
> + spinlock_t xlock; /* protect xmit */

Missing #include

> + u8 tx_buff[I3C_TTY_TRANS_SIZE];
> + u8 rx_buff[I3C_TTY_TRANS_SIZE];
> + struct i3c_device *i3cdev;
> + struct work_struct txwork;
> + struct work_struct rxwork;
> + struct completion txcomplete;

Missing #include

> + unsigned long status;
> + u32 buf_overrun;
> +};

> +static void i3c_port_shutdown(struct tty_port *port)
> +{
> + struct ttyi3c_port *sport =
> + container_of(port, struct ttyi3c_port, port);

On one line.

> +
> + i3c_device_disable_ibi(sport->i3cdev);
> + tty_port_free_xmit_buf(port);
> +}
> +
> +static void i3c_port_destruct(struct tty_port *port)
> +{
> + struct ttyi3c_port *sport =
> + container_of(port, struct ttyi3c_port, port);

Ditto.

> +static void tty_i3c_rxwork(struct work_struct *work)
> +{
> + struct ttyi3c_port *sport = container_of(work, struct ttyi3c_port, rxwork);
> + struct i3c_priv_xfer xfers;
> + u32 retry = I3C_TTY_RETRY;
> + u16 status = BIT(0);

Unnecessary initialization.

> + int ret;
> +
> + memset(&xfers, 0, sizeof(xfers));
> + xfers.data.in = sport->rx_buff;
> + xfers.len = I3C_TTY_TRANS_SIZE;
> + xfers.rnw = 1;
> +
> + do {
> + if (test_bit(I3C_TTY_RX_STOP, &sport->status))
> + break;
> +
> + i3c_device_do_priv_xfers(sport->i3cdev, &xfers, 1);
> +
> + if (xfers.actual_len) {
> + ret = tty_insert_flip_string(&sport->port, sport->rx_buff,
> + xfers.actual_len);
> + if (ret < xfers.actual_len)
> + sport->buf_overrun++;
> +
> + retry = I3C_TTY_RETRY;
> + continue;
> + }
> +
> + status = BIT(0);

Can this BIT(0) be named with a #define?

> + i3c_device_getstatus_format1(sport->i3cdev, &status);
> + /*
> + * Target side needs some time to fill data into fifo. Target side may not
> + * have hardware update status in real time. Software update status always
> + * needs some delays.
> + *
> + * Generally, target side have circular buffer in memory, it will be moved
> + * into FIFO by CPU or DMA. 'status' just show if circular buffer empty. But
> + * there are gap, especially CPU have not response irq to fill FIFO in time.
> + * So xfers.actual will be zero, wait for little time to avoid flood
> + * transfer in i3c bus.
> + */
> + usleep_range(I3C_TTY_YIELD_US, 10 * I3C_TTY_YIELD_US);
> + retry--;
> +
> + } while (retry && (status & BIT(0)));

Name with define?

--
i.